hydrogen bonding, chemistry and examples

 Hydrogen bonding

In this article, I will discuss hydrogen bonding in detail.

Definition

        The type of bond present between positive hydrogen and negative ion (highly electronegative atom), which is formed due to intermolecular forces is called a hydrogen bond.

Chemistry of hydrogen bond

       The hydrogen bond is not an actual bond. It is just an attraction between positive hydrogen ion and negative (electronegative) ion present in a molecule. It is represented by a dotted line. Those molecules which have hydrogen bonding have high melting and boiling point. It makes the molecule stronger.

Comparison of ethyl alcohol and dimethyl ether

       Ethyl alcohol and dimethyl ether have the same molecular weight but ethyl alcohol boils at 78ºC whereas dimethyl ether boils at -24ºC. The high boiling point of ethanol is associated with hydrogen bonding because dimethyl ether is no hydrogen bonding.

hydrogen bonding in ethyl alcohol

Water molecule

       Hydrogen bonding is more pronounced in the water molecules. The molecules of water are linked with each other with these intermolecular forces.

hydrogen bonding in the water molecule

Hydrogen bonding in hydrogen fluoride

       Hydrogen bonding is also present in hydrogen fluoride. Hydrogen fluoride molecules are arranged in a zigzag pattern due to hydrogen bonding.

hydrogen bonding in hydrogen fluoride

Effect of hydrogen bonding on solubility

       Hydrogen bonding also affects the hydrogen bonding of compounds. A vast majority of organic compounds easily dissolve in those solvents which are able to make hydrogen bonding.

For example:

       The solubility of o-nitrophenol in water is less as compared to its para isomer because para isomer makes hydrogen bonding with a water molecule and o-nitrophenol does not make hydrogen bonding with water molecule because, the molecule has intramolecular hydrogen bonding due to this property, volatility of compound further increases.

intramolecular hydrogen bonding in o-nitrophenol

intermolecular hydrogen bonding between water and p-nitrophenol